Checking the cut-in signal for the air conditioner compressor regulating valve N280 — AUDI

🧭 Before you start

Fits: Audi A2 (8Z)

📋 Procedure

1. Switch off the ignition.
2. Connect the operating and display unit for air conditioner/Climatronic E87 to the vehicle wiring harness.
3. Unplug the connector (A) from the air conditioner compressor.
4. Use the adapter cable from the adapter setV.A.G 1594C to restore the connection between connector (A) and the connector on the air conditioner compressor regulating valve N280.
5. Connect the probeVAS 5051/8 to the adapter leads.

6. Test lead (signal lead) to contact (2)
7. Test lead (screening) to contact (1)
8. Set the vehicle diagnostic, testing and information systemVAS 5051, to measurement mode "“DSO”" (Digital Storage Oscilloscope).
9. Setting 5V/Div =, 0.5 ms/Div (5 VDC and 0.5 milliseconds per unit)
10. Start the engine.
11. Set the temperature preselection to "“Lo”" on the operating and display unit for air conditioner/Climatronic E87.
12. On the operating and display unit for air conditioner/Climatronic E87, press the buttons "“Auto”" and "“Econ”" to actuate the air conditioning system compressor regulating valve N280 on and off.
13. In "“OFF”" or "“Econ”" mode: No square-wave signal (the air conditioner compressor regulating valve N280 is not actuated).
14. In "“Auto”" mode and at "“Lo”" temperature setting: there is a square-wave signal with a pulse width between 75% and 100% (theair conditioner compressor regulating valve N280 is actuated). [Note: The illustration shows a signal with a signal ratio of approx. 80 % .The pulse width (A) is governed by the required refrigeration capacity, the vehicle system voltage etc. (over the width of area (A), current is controlled via the air conditioner compressor regulating valve N280 by the operating and display unit for air conditioner/Climatronic E87).The signal interval (B) is always 2 milliseconds (corresponding to a frequency of 500 Hertz).The signal ratio is derived from the ratio of pulse width (A) to signal interval (B).]
15. The setting on the operating and display unit for air conditioner/Climatronic E87 and the measured ambient influences govern the pulse width of the square-wave signal (a signal ratio between 100 % and greater than 30 %, the air conditioner compressor regulating valve N280 is actuated such that compressor output required to obtain the specified temperatures is achieved). [Note: In "“Auto”" mode with a "“Lo”" temperature setting, the air conditioner compressor regulating valve N280 is actuated such that the max. permissible current of approx. 0.65 A to 0.8 A flows via air conditioner compressor regulating valve N280 (maximum compressor output).In control mode, the actuation time is governed by the required refrigeration capacity, the vehicle system voltage, etc. However, it always lasts long enough to achieve a mean current of 0.3 A.]

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